Atria tachyarrhythmias are quite common, and are seen even in patients who are not acutely ill. One such atrial tachyarrhythmia, atrial fibrillation, does not usually pose an immediate threat to the patient's life, but prolonged atrial fibrillation can compromise patient hemodynamics. Inadequate blood flow due to atrial fibrillation may lead to blood clots, which increase the risk of strokes. Other symptoms may include palpitations of the heart, dizziness, or loss of consciousness.
One method of treating atrial fibrillation is to deliver a countershock to terminate the arrhythmia. For example, the countershock may be applied via an external or implantable defibrillator. However, this method of treating atrial fibrillation risk causing ventricular tachyarrhythmias, including life-threatening ventricular fibrilation.
One method of reducing the risk of ventricular fibrillation is by synchronizing the delivery of a countershock to an electrical ventricular activation (R-wave) of the heart. There is, however, a need in the art to further reduce the risk of inducing ventricular tachyarrhythmias, such as life-threatening ventricular fibrilion, during the countershock treatment of comparatively less exigent atrial tachyarrhythmias.